Rock bit decoupler

ABSTRACT

A rock bit decoupler adapted to provide an axially releasable rotary driving connection between a string of drill pipe and a rock bit. It is designed so that when the rock bit is held away from the work surface, a clutch has an engaged condition permitting rotation of the drill pipe and rock bit in unison; and when the rock bit is forced against the work surface, the clutch obtains a disengaged condition enabling rotation of the drill pipe relative to the rock bit and simultaneously enabling the drill pipe to transmit force pulses to the rock bit. In one embodiment, a jaw clutch is used. In a second embodiment, a cone clutch is used.

1 1 Oct. 14, 1975 United States Patent 1191 Amtsberg ROCK BIT DECOUPLER Primary Examiner-Frank L. Abbott 75 1 t Lest A. Amtsbe Ut N.Y. nven or er rg lca Assistant Examzner-W1ll1am F. Pate, 111 [73] Assignee: Chicago Pneumatic Tool Company,

Attorney, Agent, or FirmStephen J. Rudy New York, N.Y.

Mar. 28, 1974 Appl. No.: 455,587

ABSTRACT [22] Filed:

A rock bit decoupler adapted to provide an axially releasable rotary driving connection between a string of [52] US. Cl. 173/131; 64/29; 173/13 drill pipe and a rock bit. It is designed so that when the rock bit is held away from the work surface, a

[51] Int. E21B 11/02 173/131, 13, 163, 306; 175/321, 101, 320; 64/29; 192/89 W [58] Field of Search clutch has an engaged condition permitting rotation of the drill pipe and rock bit in unison; and when the rock bit is forced against the work surface, the clutch [56] References Cited obtains a disengaged condition enabling rotation of UNITED STATES PATENTS the drill pipe relative to the rock bit and simultaneously enabling the drill pipe to transmit force pulses to the rock bit.

In one embodiment, a jaw clutch is used.

In a second embodiment, a cone clutch is used.

39 now 34 m 6 1,391,723 9/1921 Du Sell 2,067,377 1/1937 Burns et a1... 3,132,707 5/1964 Alexander.... 3,802,518 4/1974 FOREIGN PATENTS OR APPLICATIONS 1,151,477 7/1963 Germany 175/320 4 8 Drawmg F'gures ROCK BIT DECOUPLER BACKGROUND OF THE INVENTION This invention relates to the drill pipe string of a rock drill; and it has for its general object to provide an improved means for coupling a string of drill pipe to the rock bit so that the drill pipe is enabled to rotate relative to the rock bit when the latter is impinged against the work surface.

In known rock drills, a rock bit is carried at the end of a string of drill pipe. Lengths of drill pipe are added to the string as the bit progressively deepens the drill hole. The lengths are threadedly joined to one another and to the rock bit. The rock drill also has a piston which is reciprocable to transmit through the drill string thrusts to the bit to break up the rock. A motor mounted to the rock drill is operable to transmit rotary motion through the drill string to the rock bit.

Excessive torque accompanying heavy drill string thrusts causes rapid wear of the bit; and also causes excessive tightening of the threaded joints used to connect the sections of drill pipe. Excessive tightening of the drill pipe increases the usual difficulty of later loosening the pipe joints when withdrawing the drill string from the drill hole. The motor employed to rotate the drill string and the bit that the string carries does not have a high torque capability at a steady state of operation, but momentum developed by the motor plus the momentum of the rotating drill pipe during a drill operation can cause a high torque pulse to be imparted to the bit and to the joints of the drill string when rotation of the bit is momentarily stopped by impingement with the work surface. It is this high torque that causes undesirable excessive tightening of the pipe joints and undesirable wear of the rock bit.

Accordingly, it is an object of this invention to avoid an excessive torque force being imparted to the drill pipe and to the bit that would otherwise prevail during the time and bit is forced into the work surface by thrust pulses from the drill pipe.

This objective is accomplished in the present invention by the provision of a decoupler, or declutching unit, designed to provide a releasable rotary driving connection of the drill pipe with the rock bit. It functions during the conditions earlier mentioned to release the rotary driving connection of the drill pipe from the bit. When the driving connection is thus released, the drill pipe can rotate relative to the bit with very low torque transmission while the bit is held embedded in the work surface; and when thus released, the drill pipe is enabled to transmit axially directed thrusts to the rock bit without undesirable excessive torque.

The foregoing, as well as other features, objectives and advantages of this invention will appear more fully after considering the detailed description which follows in conjunction with the accompanying drawings wherein the invention is illustrated. It is to be expressly understood, however, that the drawings are for purposes of illustration and description and, accordingly, they are not to be construed as delineating the scope of the invention.

BRIEF DESCRIPTION OF THE DRAWING In the accompanying drawing: FIGS. -l4 illustrate a first embodiment of the invention in which:

FIG. 1 is a view in longitudinal section illustrating the invention applied to a drill pipe string of a rock drill and showing the decoupler element in an engaged condition;

FIG. 2 is a view similar to that of FIG. 1 but showing the decoupler in a disengaged condition;

FIG. 3 is a detail in plan of the driving clutch member; and

FIG. 4 is a detail in plan of the driven clutch member.

FIGS. 5-7 illustrate a second embodiment of the invention in which:

FIG. 5 is a fragmentary view wherein the jaw clutch shown in FIG. 1 has been replaced by a cone clutch;

FIG. 6 is a detail in plan of the driving cone clutch member;

FIG. 7 is a detail in plan of the driven cone clutch member; and

FIG. 8 illustrates the cone clutch members of FIG. 5 as being integral with their related supports.

DESCRIPTION OF A FIRST EMBODIMENT OF THE INVENTION Reference is now directed to FIGS. 1-4 of the drawing wherein there is illustrated a rock bit decoupler or declutching unit, generally designated 10. It is adapted to be axially aligned with, and coupled at one end to, a string 11 of drill pipe of a rock drill. It is adapted to be coupled at its opposite end with a rock bit 12.

The rock bit is of a conventional type having a cutting face 13 at its bottom, and cutting side surfaces 14. The outer diameter of the head of the cutting end of the bit is made greater than that of the drill string so that the hole being drilled will obtain a diameter adequate to allow the cutting to be blown out of the hole.

The drill string is connected to a rotation motor (not shown) whereby it is caused to be rotated continuously during a drilling operation.

The decoupler 10 has a tubular body or coupling 15 providedwith an open upper end which has an internal threaded joint or connection 16 with a pin 17 of a drill pipe adapter 18. The latter, in turn, has a threaded central socket 19 in its upper end adapted to be threadedly joined with the depending pin 21 of the next adjoining length of drill pipe 9 in the string 11.

Within the interior of the coupling 15, driving and driven clutch members 22 and 23 are arranged to obtain a releasable rotary driving connection of the drill string 11 through the coupling with a cylindrical rock bit rod, or adapter, 24 carrying the rock bit.

The driving clutch member 22 is of ring form (FIGS. 1-3). It is seated upon an annular internal shoulder 25 of the coupling and is rigidly held attached to the latter by means of a group of press fitted pins 26, here three in number. It has an annular upper surface faced with clutch jaws 27 circumferentially separated from one another by spaces 28.

The driven clutch member 23 is also of ring form (FIGS. 1, 2, 4). It sleeves a smooth cylindrical surface portion 29 of the rock bit rod; and it is seated upon an annular undershoulder 31 of a collar part 20 of the rod. It is held rigidly attached to the collar by means of a group of press fitted pins 32, here three in number. It has an annular undersurface which is faced with jaws 33 and separating spaces 34 adapted to axially interengage with the spaces and jaws of the driving clutch member.

A desirable advantage obtained by the pinned retention arrangement of the clutch members with the adapter rod and the coupling is that a punch may be applied to the retaining pins 26 and 32 through holes 30 to knock out the pins when needed to allow easy replacement of the clutch members.

The jaws of the clutch members have (as appears in FIGS. 1-4) flat outer faces and perpendicular or vertically walled sides. This form of the jaws is preferable as it obtains a positive locking of the jaws with one another and it avoids camming torque release of the jaws as might otherwise occur were the jaws and spaces between them sloping or rounded. Further, the dimension of the spaces 28, 34 between the jaws in each clutch member are greater in their lateral or circumferential direction than the corresponding dimensions of the jaws to be received therein. The spaces in this respect are approximately twice as great. This is desirable so as to allow easy axial engagement and axial release of the jaws, as well as a desirable slight angular lost motion of the jaws relative to one another during engagement.

The smooth surface portion 29 of the rock bit rod extends loosely through the driving clutch member 22 and slidably through an axial hole 37 formed in a bottom wall of the coupling. An externally threaded portion of the adapter rod is threadedly jointed as at 39 in an axial socket of the rock bit.

A clutch compression spring 40, disposed between opposed annular shoulders 41 and 42 respectively of the collar of the rock bit rod and an opposed end of the adapter pipe 18, constantly urges the driven clutch member into axial engagement with the driving clutch member, as in FIG. 1. In the engaged condition of the clutch, torque provided by the rotating drill string 11 will be transmitted to the rock bit rod 24 and to the rock bit 12 in such manner that the rock bit will be rotated in unison with the drill string. The clutch will have, or obtain, this engaged condition when the rock bit is moved out of contact from the work rock.

The drill string and the rock bit rod have limited axial movement or lost motion relative to one another in order to obtain at certain times a disengaged condition of the clutch to enable the drill string to rotate relative to the rock bit rod and the bit. The extent of this disengaging movement is small. It corresponds to a space 44, existing only in the engaged condition of the clutch (FIG. 1), between a flat thrust receiving surface 45 of the rock bit rod and an opposed corresponding thrust transmitting surface 46 of the drill pipe adapter.

When the space 44 has been closed or taken up by a lost motion downward movement of the drill string against the opposed force of spring 40 relative to the rock bit rod, (as in FIG. 2) the clutch will be disengaged and the end surfaces 45, 46 of the drill pipe adapter and rock bit rod will abut one another. The abutting end surfaces will then permit pulses or thrusts generated by downward movement of the drill string to pass directly from the drill pipe through the rock bit rod to the bit; and at the same time the drill pipe will be enabled to rotate relative to the rod.

In summary of the functioning of the decoupler unit in the drill string: When the drill string holds the rock bit out of contact with the work rock (as explained earlier) the clutch members will be engaged, as in FIG. 1, enabling the rock bit to be rotated through the clutch in unison with the drill string. Subsequent downward movement of the drill string accompanied by a normal force pulse (usually more than 10 tons developed by a piston member of the rock drill) will bring the bit into an initially light contact with the rock. The drill pipe will, however, continue moving downward relative to the rock bit rod with lost motion to the extent permitted by the space 44. Upon the latter being taken up, the clutch jaws will have axially disengaged and, simultaneously, the opposed faces 45, 46 of the rock bit and pipe adapter will contact one another. The full force of the thrust pulse of the downwardly moving drill pipe will then be transmitted directly through the contacting faces 45, 46 to the rock bit. The rock bit will then become embedded in the rock, but at this time the clutch will be disengaged and the drill string will be rotating relative to the rock bit, transmitting to the latter only an ineffective low torque resulting from the frictional relation between the contacting faces and 46. Full clutch disengagement occurs momentarily before the lost motion space is fully taken up. The strong torque that would (except for the decoupler) have been transmitted to the rock bit and to the drill string is avoided. Accordingly, the undesirable excessive tightening of the threaded joints of the drill pipe and the undesirable wear upon the cutting face of the rock bit that would have otherwise occurred is avoided by the provision of the decoupler in the drill string.

As the drill pipe is next drawn away from the rock, the clutch spring 40 relaxes or re-expands to press the rock bit rod 24 forwardly relative to the drill pipe to reengage the clutch members. With this action, the rotating drill string is again permitted to transmit its rotation through the engaged clutch to the rock bit.

The usual blow passage 43 extends through the drill string and rock bit to allow pressure air to be blown in conventional manner to the bottom of the hole to clear it of debris.

As best appears in FIGS. 1 and 2, the axial depth of engagement of the clutch jaws is small or shallow. And the axial distance the jaws are required to move out of engagement is only slightly greater, corresponding to the limited space 44. This arrangement is of advantage in that it obtains swift clutching and declutching action when needed. Release of the clutch occurs momentarily before the lost motion space 44 is fully taken up.

The spring 40 is constantly exerting a strong force both in the direction of the rock bit rod and the drill pipe urging them in opposite directions, serving to bring the clutch members into engagement with one another. This tendency to engage the clutch members results in their engagement as the downward pressure of thrusts upon the drill pipe is relaxed.

The broad axial area presented by the periphery of the collar 20 to the internal wall of the coupling, together with the broad axial area presented by the hole 37 to the rock bit rod, guide the rock bit rod and the coupling 15 in the relative axial movement of one to the other without undesirable accompanying side play or wobble.

FIG. 5 EMBODIMENT In the embodiment (FIGS. 5-7), the jaw clutch of FIG. 1 has been replaced by a two-part cone clutch 47 comprising an annular female driving clutch member 48 having an internal coned surface 49 adapted to move into clutched frictional engagement with a complementary mating external coned surface 50 'of an annular driven male clutch memberSI, as indicated in FIG. 5. The clutch members are retained on their respective supports by press fitted pins 26, 32.

While the clutch elements have been illustrated as being detachably associated with their related supports, they may be made integral with the latter. This is illustrated by way of example with respect to the cone clutch 47a in FIG. 8 wherein the driving clutch element 48a is an integral part of the coupling a, and the driven clutch element 49a is an integral part of the rock bit rod 29a.

The invention illustrated in the various embodiments is particularly suited for use in a string of drill pipe of a rock drill of a type wherein the string of drill pipe receives its rotation from a rotary fluid powered motor; amd wherein a fluid powered reciprocable piston is operable to reciprocate the drill string toward and away from the work rock.

While the invention has been illustrated in several embodiments and described in detail herein, it is to be expressly understood that the invention is not limited thereto. Various changes can be made in the design and arrangement of the parts thereof without departing from the spirit and scope of the invention; accordingly, it is my intent to claim the invention not only as shown and described herein but also in all such forms and modifications as may reasonably be construed to fall within the spirit of the invention and the scope of the appended claims.

What is claimed is:

l. The combination comprising a continuously rotating string of drill pipe having an impact transmitting face at its bottom end, a rock bit rod having an impact receiving face at its upper end in opposed normally spaced relation to the impact transmitting face and carrying at its opposite end a rock bit, a spring load, clutch means carried in part by the pipe and in part by the rod normally engaging under the spring load the pipe with the rod for transmitting the rotation of the pipe to the rod and normally spacing the impact transmitting face axially clear of the impact receiving face during transmission of rotation of the pipe to the rod, and the clutch means being responsive to downward axial movement of the pipe relative to the rod against the spring load to disengage the pipe from transmitting its rotation to the rod and to simultaneously allow the impact transmitting face of the pipe to move into impacting relation with the impact receiving face of the rod.

2. The combination as in claim 1, wherein the string of drill pipe includes a coupling connected to its lower I end having an open upper end into which the impact transmitting face axially depends, the rod includes a shank depending slidably through a bottom axial opening of the coupling, a part of the clutch means is carried internally by the coupling, and an opposed mating part of the clutch means is carried by the upper end of the rod.

3. The combination as in claim 2, wherein an adapter section of the string of drill pipe has an axially depending pipe portion of reduced diameter upon which the impact transmitting face is formed, and the rod includes an upwardly extending rod portion of reduced diameter upon which the impact receiving face is formed.

4. The combination as in claim 3, wherein the spring load is located in the coupling between an overlying shoulder of the adapter in surrounding relation to the depending portion of the adapter and an underlying shoulder of the rod in surrounding relation to the upwardly extending rod portion. 

1. The combination comprising a continuously rotating string of drill pipe having an impact transmitting face at its bottom end, a rock bit rod having an impact receiving face at its upper end in opposed normally spaced relation to the impact transmitting face and carrying at its opposite end a rock bit, a spring load, clutch means carried in part by the pipe and in part by the rod normally engaging under the spring load the pipe with the rod for transmitting the rotation of the pipe to the rod and normally spacing the impact transmitting face axially clear of the impact receiving face during transmission of rotation of the pipe to the rod, and the clutch means being responsive to downward axial movement of the pipe relative to the rod against the spring load to disengage the pipe from transmitting its rotation to the rod and to simultaneously allow the impact transmitting face of the pipe to move into impacting relation with the impact receiving face of the rod.
 2. The combination as in claim 1, wherein the string of drill pipe includes a coupling connected to its lower end having an open upper end into which the impact transmitting face axially depends, the rod includes a shank depending slidably through a bottom axial opening of the coupling, a part of the clutch means is carried internally by the coupling, and an opposed mating part of the clutch means is carried by the upper end of the rod.
 3. The combination as in claim 2, wherein an adapter section of the string of drill pipe has an axially depending pipe portion of reduced diameter upon which the impact transmitting face is formed, and the rod includes an upwardly extending rod portion of reduced diameter upon which the impact receiving face is formed.
 4. The combination as in claim 3, wherein the spring load is located in the coupling between an overlying shoulder of the adapter in surrounding relation to the depending portion of the adapter and an underlying shoulder of the rod in surrounding relation to the upwardly extending rod portion. 